This is a proposal to investigate the relationship between melanotic-expression, growth activities, and various aspects of tumorigenesis and malignancy in experimental melanoma tumors of the Syrian hamster. Benign "blue nevus"-like tumors will be induced with 7,12-dimenthylbenz(a)anthracene and other chemical carcinogens, and these tumors will be made malignant by transfer to other hosts. Melanotic expression of tumors will be examined as rates of melanin biosynthesis, melanin content, tyrosinase activity, and tyrosine pool size; rates of growth and metabolism as rates of radioactive thymidine, L-valine, and D-glucose incorporations. Normal and albino animals will be used to evaluate the effect of chemical carcinogens on melanotic expression in the premalignant benign lesion. Feeding experiments with L-dopa will test the relation of melanotic stimulation to malignant transformation. Correlations of malignancy and melanotic activity in many different tumors will be used to establish the interdependency of these properties in fully differentiated tumors.